December 18, 2014

US Weather Bureau is predicting 2-5 inches of rain for here Saturday night. That should be fun. (Also 5-8 inches in the Coast range.)

Where that won't be fun is if the Willamette goes out of its banks. It won't affect us here, but the creek ought to get pretty lively!

UPDATE: I wonder if this will be as bad as the Chrismas Flood? Probably not, but it may come close.

UPDATE: I was only 10 when the Christmas Flood happened, but it's got special meaning to me. It was the second part of a 1-2 punch to hit the Northwest, coming just about a year after what we call the Columbus Day Storm.

About 1961, my parents bought a lot in SW Portland, moved a trailer house onto it, and began building their dream house. Now when a lot of people say "We're building a house" they mean they hired a construction company. That's not what we did. My dad actually designed the place and drew all the blueprints, and worked on it evenings and weekends and vacations. My grandfather, who was a carpenter, came up to help as much as he could, and friends of my dad would sometimes come over and help. My brother, who was 12-13 years old at the time, did a lot of work and me, 8-9, I did as much as I could. We had the foundation poured and the basement covered by the main floor, and managed to put up all the outer walls and got the roof over it, and covered the whole roof with plywood. But there weren't yet any internal partitions by October, 1962.

And then we got the storm of the century, and it blew the house down. I was in the bathroom when it happened so I didn't see it go. But shortly thereafter my folks began to worry that the trailer might roll over in the wind, and so we walked to our neighbor's house and asked them to put us up for the night.

We spent a week living at my uncle's house in NE Portland because his electricity didn't go out. It took us several months to tear everything apart and restack all the lumber, and then to put the walls and roof back up again.

We were a lot further along by a year later when the second punch of the 1-2 whammy happened. It was bad for the state, but it didn't actually affect us at all. (Our lot was on the edge of the Tryon Creek Valley, so the water just ran off and we never saw anything.

But I remember in 1964 people beginning to wonder if we'd get slammed again. (We didn't.) By then we were living in the house and had sold the trailer.

UPDATE: Oh, boy; they've updated the forecast:

LATEST FORECASTS FOR FRIDAY NIGHT THROUGH MONDAY AFTERNOON BRING 8 TO 12 INCHES OF RAIN TO THE CASCADES AND FOOTHILLS...7 TO 11 INCHES FOR THE COAST RANGE...5 TO 7 INCHES ALONG THE IMMEDIATE COAST...AND 3 TO 4 INCHES ALONG THE I-5 CORRIDOR.

That last is me.

And if those estimates are even close to accurate, every river in the western third of this state is going to flood.

I don't recall anybody at work freaking out about the forecast...though I've been busy with other things and I'm not plugged in to the operations side on even a normal basis.

I do know that there have been some flood control projects completed in the Willamette watershed since 1964. They've had their pools drawn down for a while now, and can absorb quite a bit (though the dams won't help for rain below them)

I assume that places like the Detroit dam have lowered their level in preparation, and probably some of the big dams on the Columbia. But there are no dams on the Willamette and Tualatin rivers, or the Marys River, and there are no dams below Detroit on the Santiam river.

When I was in college I lived my first two years in a trailer park south of town, right on the edge of the Marys river. One winter we had some flooding and the Willamette river went out of its banks, which backed up the Marys river. Most of the trailer park was flooded (It turned out my trailer was parked on the absolute highest point in the park, and I just got a few inches of water below me). 99W south of Corvallis was at least two feet deep for a couple of days.

Something like that could happen again this time. Looks like the heavy rain is going to be spread out over a couple of days, though, so maybe there will be enough time for water to drain out to keep things from getting really bad.

We'll find out starting tomorrow; the forecast is for 3/4 - 1 inch of rain tomorrow, and then again on Sunday, plus lesser rain tomorrow night and Sunday night.

The lower Columbia dams are run of the river, and don't have variable storage. If 250,000 cfs comes in to them, 250,000 cfs goes out. I was out at John Day on Wednesday, and they only had a couple of feet between the forebay pool and the tops of the Tainter gates that control the spillway. I don't think that The Dalles or Bonneville are much different. If they varied their forebay levels too much it would wreak havoc on the fish ladders and navigation, especially at locks.

Willamette Valley only has flood control on some tributaries, so if there's enough rain on the river valley itself, yeah, there's not a whole lot to be done.

I thought Big Cliff reregulated for Detroit, but I've not been out there myself and I could be misremembering. Granted, it may not have much storage.

Posted by: CatCube at December 20, 2014 08:13 AM (fa4fh)

4
The Detroit Dam pool can be lowered 36 meters in preparation for floods. But that's just the North Santiam river, which is only a small part of the Willamette drainage.

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